1,3-propanediol can be used as a raw material for synthesizing polyester, polyether or polyurethanes and is used in various applications, including fibers, such as highly functional clothes, carpets or automotive fabrics, and plastic films. In particular, polytrimethylene terephthalate (PTT) that is produced by polymerization of 1,3-propanediol with terephtalic acid has excellent physical properties and a melting point of 228° C. which is lower than that of polyethylene terephthalate (PET). Thus, polytrimethylene terephthalate has high utility and is receiving as a next-generation fiber material capable of substituting for PET. Also, the plastics and polymers produced from 1,3-propanediol as a monomer show excellent optical stability compared to the products produced from butanediol or ethylene glycol. In addition, 1,3-propanediol can be used as a polyglycol-type lubricant and a solvent, and thus its commercial value is evaluated to be higher than that of glycerol.
1,3-propanediol can be produced by chemical synthesis or microbial fermentation. Chemical processes for producing 1,3-propanediol include a process of converting ethylene oxide to 1,3-propanediol by hydroformylation (U.S. Pat. No. 3,687,981) and a process of converting acrolein to 1,3-propanediol by hydration (U.S. Pat. No. 5,015,789). However, such chemical processes have problems in that they require a high-temperature or high-pressure process during the production of 1,3-propanediol, leading to high production costs, and generate waste oil containing environmental pollutants.
Biological processes include a process of producing 1,3-propanediol from glycerol using microorganisms such as Citrobacter, Clostridium, Enterobacter, Klebsiella, Lactobacillus or the like, which are facultative anaerobic strains (U.S. Pat. No. 5,254,467).
In a metabolic process of converting glycerol to 1,3-propanediol using the above microorganisms, various kinds of oxidation metabolites are produced in large amounts. Particularly, 2,3-butanediol which is an oxidative metabolite of glycerol has a boiling point similar to 1,3-propanediol, and thus acts as a great hindrance in a process of purifying 1,3-propanediol. Previously, the present inventors attempted to use a metabolic engineering technique to develop microorganisms which produce only 1,3-propanediol in glycerol metabolism without producing byproducts of oxidative metabolism, including 2,3-propanediol, and as a result, the present inventors used a genetic recombinant technique to construct a mutant in which the oxidative metabolic pathway that produces byproducts in the glycerol metabolic pathway had been blocked so that the mutant has only the reductive metabolic pathway that produces 1,3-propanediol (Korean Patent Application No. 10-2008-0122166). However, it was found that the constructed mutant had low production of 1,3-propanediol, although it produced no byproducts in general batch culture.
Accordingly, the present inventors constructed a mutant strain in which the oxidative metabolic pathway that produces byproducts in the glycerol metabolic pathway had been blocked and have made extensive efforts to increase the production of 1,3-propanediol in culture of the mutant.
As a result, the present inventors have found that, when a two-step culture process is carried out which consists of a first-step culture process in which glycerol is not added to medium and a second-step culture process in which glycerol is added to medium, the yield of 1,3-propanediol will increase, thereby completing the present invention.